The elevator system is usually integrated in a building. For this purpose the building comprises a shaft which extends over several floors of the building. The elevator system comprises at least one elevator car. The elevator car is moved by means of a drive unit along substantially vertical guide rails in the elevator shaft. In tall buildings lower regions of the building are already fitted with a functional elevator system whilst upper regions of the building are still under construction. In this case, special so-called co-growing elevator systems are used. This means that during the construction period of the building, a machine room of the elevator system is moved from a lower temporary usage position in the elevator shaft to a next upper usage position in the elevator shaft. The machine room is accordingly configured as a movable machine platform. In this case, it is important inter alia that this machine platform is balanced out during its displacement in the elevator shaft.
The movable machine platform can also be used to receive or to transport other elevator components. Usually at least one end roof is located above the machine platform at the end of the respective building section. Above the end roof, the building can be constructed further whilst the elevator car is already operating below the machine platform, i.e. can be moved.
As soon as a next-higher travel region of the elevator shaft is completed, the necessary elevator components such as for example the guide rails can be installed above the machine platform in the elevator shaft. When the next-higher travel region is ready, the machine platform can be moved so that this next-higher travel region or a corresponding part of the building can be made accessible to the elevator car. Since the building is constructed from bottom to top, the machine platform is usually moved from a lower temporary usage position to an upper optionally temporary usage position.
Such a movable machine platform is usually supported or anchored by means of settling devices such as supports or rests on a side wall of the elevator shaft or in recesses in the wall of the shaft.
Usually the machine platform can be lifted by means of a chain hoist in the elevator shaft. Such a heavy chain hoist is located above the machine platform. Consequently a disadvantage is that the installation of the chain hoist above the machine platform requires a great effort. In addition the installation of the guide rails which is continued directly above the machine platform by a working platform is made difficult since the chain of the chain hoist is arranged approximately centrally within the horizontal elevator shaft cross-section along the elevator shaft. Furthermore, for the furthest possible raising of the machine platform by the winding up of the chain, a minimum distance is required between the machine platform and the installation site of the chain hoist.